The Endocrine System

What is the system? Made up of glands that produce and secrete hormones (chemical messengers) Regulation of growth, metabolism, sexual development Responses to stress and injury Internal balance of body systems (homeostasis)

11.4 Control of Hormones Negative feedback system When the hormone levels rise, the organ that secretes the hormone is switched off

BIG IDEA: HORMONES are chemical MESSENGERS that act on target cells

Major Structures

Example of Negative Feedback

Positive Feedback System

11.5 Pituitary Gland 22 = Thalamus 24 = Hypothalamus

Hormone Control The pituitary is often called the “master gland” because it controls all of the other glands. Its actions are controlled by the hypothalamus in the brain.

Growth hormone or GH - GH stimulates growth in childhood and is important for maintaining a healthy body composition. In adults it is also important for maintaining muscle mass and bone mass. It can affect fat distribution in the body.

That’s a bull of the Belgian Blue breed, which has a genetic anomaly that suppresses the production of a hormone called myostatin that inhibits muscle growth – hence the ‘double muscling’ seen above. Myostatin inhibitor drugs are being developed with the intent of treating muscle-wasting diseases like muscular dystrophy in humans.

Problems with the pituitary gland can result in Dwarfism Primordial Dwarfism

Or a person can grow too much Or a person can grow too much. These are pictures of the man known as “The Alton Giant”, Robert Wadlow. Robert was 8’11”

Adrenocorticotropin or ACTH - ACTH stimulates production of cortisol by the adrenal glands. Cortisol, a so-called "stress hormone," is vital to survival. It helps maintain blood pressure and blood glucose levels. Many diet aids claim that they block cortisol levels. Cortisol from stress may lead to fat deposits in the belly.

Thyroid-stimulating hormone or TSH - TSH stimulates the thyroid gland to make thyroid hormones, which, in turn, control (regulate) the body's metabolism, energy, growth and development, and nervous system activity.

Luteinizing hormone or LH - LH regulates testosterone in men and estrogen in women. (gonadotropin)

Follicle-stimulating hormone or FSH - FSH promotes sperm production in men and stimulates the ovaries to release eggs (ovulate) in women. LH and FSH work together to allow normal function of the ovaries or testes. (gonadotropin)

Posterior Pituitary Hormones Oxytocin - Oxytocin causes milk letdown in nursing mothers and contractions during childbirth.

THYROID GLAND The thyroid hormones control your metabolism, which is the body's ability to break down food and store it as energy and release of energy TED-Ed Video on the Thyroid

THYROID HORMONES Thyroxin (T4) & Tri-iodothyronine (T3) - both increase the rate at which cells release energy from carbohydrates Calcitonin – regulates the blood concentration of calcium BMR – basal metabolic rate : how many calories the body must consume to maintain life BMR Calculator

Problems with the Thyroid Iodine is essential for the formation of thyroxine. Lack of iodine causes a swelling of the thyroid → GOITER. Iodine is only found in seafood, so if salt wasn’t iodized, a lot of people wouldn’t get enough iodine, and there would be a lot of goiters.

Goiter

Hypothyroidism Before and After Treatment

Cretinism (hypothyroidism in infants)

Hyperthyroidism (Grave’s Disease)

Exposure to radioactive iodine in childhood is also believed to be associated with thyroid cancer. Following the Chernobyl nuclear power plant explosion, there was an increase in thyroid cancer in children.

Parathyroid Glands Located behind the thyroid, four tiny glands Parathyroid Hormone (PTH) - takes calcium from the bones to make it available in the blood

Adrenal Glands Located at the top of the kidneys   Adrenal Cortex - outer area Adrenal Medulla  - inner area Adrenal Glands = Adrenaline

Adrenal Medulla Epinephrine & Norepinephrine – increased heart rate, breathing rate, elevated blood pressure (fight or flight, response to stress) People with severe life threatening allergies often carry injectors

Adrenal Cortex Aldosterone – helps kidneys conserve sodium and excrete potassium, maintaining blood pressure Cortisol – keeps blood glucose levels stable Adrenal Sex Hormones - androgens (male) and estrogens (female)

Adrenal Gland Disorders Cushing’s Disease Hyperadrenocorticism Increased thirst and urination Increased hunger Increased panting Pot-bellied abdomen Obesity Loss of hair Cushings can be caused by a benign pituitary tumor (most common), a tumor on the adrenal glands, or overuse of steroids (often used to treat allergies or autoimmune disease) https://www.vetdepot.com/article-images/cushings-disease.gif Cushing's syndrome happens when the adrenal glands makes too much cortisol.

Addison’s disease Hyposecretion of cortisol Low blood pressure results Increased pigmentation

Pancreas The pancreas is a large gland behind your stomach that helps the body to maintain healthy blood sugar (glucose) levels. Contains islands of cells called the Islets of Langerhans which secrete glucagon and insulin

Glucagon – stimulates the liver to break down glycogen, raises blood sugar concentration Insulin – decreases blood sugar concentrations, affects the uptake of glucose by cells *Both hormones work together to maintain a balance in the blood sugar

Diabetes Diabetes Mellitus – results from an insulin deficiency, blood sugar rises (hyperglycemia) and excess is excreted in the urine. Type I - insulin dependent diabetes mellitus or juvenile onset diabetes, often caused by inherited immune disorder that destroys pancreatic cells

Type II – mature onset diabetes (usually after the age of 40), often individuals are overweight, can be controlled with diet and exercise Blood sugar test, device pricks the finger and measures the amount of sugar in the blood

Injection of insulin will lower the blood sugar levels Hypoglycemia can occur if levels become too low, can be cured with direct injection of glucose or with eating something high in sugar. This is why diabetics often have candy.

Gestational Diabetes Pregnancy hormones can block insulin from doing its job. When this happens, glucose levels may increase in a pregnant woman's blood. Gestational diabetes usually starts halfway through the pregnancy. All pregnant women should receive an oral glucose tolerance test between the 24th and 28th week of pregnancy to screen for the condition.

Other Endocrine Glands Pineal Gland – located between the cerebral hemispheres, secretes melatonin, maintains Circadian rhythms (light and dark activity)

Can you find the hypothalamus? Pituitary?

Thymus Gland – large in young children, gradually shrinks with age, secretes thymosins, important to immune function

Reproductive Glands – testes and ovaries – testosterone, progesterone, estrogen GONADOTROPINS - include any hormone that affect the gonads

Steroids Anabolic steroids are artificially produced hormones that are the same as, or similar to, androgens, the male-type sex hormones in the body. There are more than 100 variations of anabolic steroids. The most powerful androgen is testosterone.